Romans 9:15-19

For God said to Moses, “I will show mercy to anyone I choose, and I will show compassion to anyone I choose.” So it is God who decides to show mercy. We can neither choose it nor work for it. For the Scriptures say that God told Pharaoh, “I have appointed you for the very purpose of displaying my power in you and to spread my fame throughout the earth.” So you see, God chooses to show mercy to some, and he chooses to harden the hearts of others so they refuse to listen. Well then, you might say, “Why does God blame people for not responding? Haven’t they simply done what he makes them do?”